(1) Field of Invention
The present invention relates to a process used for fabricating Si-on-diamond or on diamond-like-carbon (DLC) wafers, and more particularly, Si-on-diamond or on DLC wafers that can be used as thermal management substrates.
(2) Description of Related Art
Silicon (Si) wafers have long been used as substrates for fabricating circuits, such as Ultra Large Scale of Integration (ULSI) circuits. The Si wafers have typically been homogeneous Si monocrystalline wafers and separation by implantation of oxygen (SIMOX) wafers.
High speed ULSI Complimentary Metal Oxide Semiconductor (CMOS) digital Integrated Circuits (ICs) generate more heat per unit chip area as levels of integration and clock rates are increased. Heat management is currently one of the major considerations in designs of ULSI digital ICs. Effective heat management will become increasingly more important as IC integration starts expanding into a third dimension. The efficiency with which heat is dissipated from digital ICs is currently limited by thermal conductance properties of the Si substrate. A solution for solving heat management problems would be to fabricate Silicon based ICs on a substance with increased thermal conductor, such as diamond. The heat conductance of diamond of 20 W/(cmK) is higher than that of Silicon by a factor of 13.
There are several patents issued that are related to Silicon-on-diamond technology. U.S. Pat. No. 5,376,579, issued to Annamalai (hereinafter referred to as “The Annamalai Patent”), describes a process for fabricating Si-on-diamond substrates. However, the The Annamalai Patent, describes Si-on-diamond substrates being bonded to a carrier wafer, because they do not posses sufficient mechanical strength to survive normal handling. U.S. Pat. No. 5,782,975, issued to Linn (hereinafter referred to as “The Linn Patent”), describes a method for fabricating Si-on-diamond substrates by bonding of chemical vapor deposition (CVD) diamond to Silicon. However, the thermal contact between the Si and the diamond substrate taught by The Linn Patent does not provide for sufficient thermal contact because the two layers are not epitaxially fused together.
Thus, a continuing need exists for a fabrication process that forms a Si structure epitaxially fused to a diamond, or to a (diamond-like-carbon) substrate to increase thermal contact and that can used as a thermal management substrate.